Method of manufacturing an optical fibre, preform and optical fibre

Abstract

A method for manufacturing an optical preform via an internal vapour deposition process, wherein during the inside deposition process the velocity of the reaction zone is set so that the velocity of the reaction zone over the length of the supply side-to-discharge side is higher than the velocity of the reaction zone over the length of the discharge side-to-supply side.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims priority to Dutch Patent Application No. 2006472 filed Mar. 25, 2011, the contents of which are incorporated by reference herein.TECHNICAL FIELD AND BACKGROUND OF THE INVENTION[0002]The present invention relates to a method of manufacturing an optical fibre including the following steps:[0003]i) providing a hollow substrate tube,[0004]ii) passing doped or undoped reactive, glass-forming gases through the interior of the hollow substrate tube,[0005]iii) creating such conditions in the interior of the hollow substrate tube that deposition of glass layers onto the interior of the hollow substrate tube takes place, wherein a non-isothermal plasma is reciprocated between two reversal points along the substrate tube, wherein the velocity of movement of the plasma decreases to zero from each deceleration point to each reversal point,[0006]iv) subjecting the substrate tube thus obtained to a collapsing treatment so as to fo...

AI Technical Summary

Benefits of technology

[0038]In a preferred embodiment the velocity of the reaction zone over the length supply side—discharge side is within the range of 2 m / min-40 m / min, preferably 15 m / min-25 m / min. In case the velocity of the reaction zone is less than 2 m / min, the deposition efficiency of dopants tends to drop to a very low value, which is undesirable. The present inventors assume that a low velocity of the reaction zone the temperature inside the hollow substrate tube will be too high, resulting in a negative effect on the deposition efficiency of dopants. If the velocity of the reaction zone is above the aforementioned upper limit, several problems with the deposition apparatus will probably occur, especially in the area at the reversal points. The velocity of the reaction zone at each of the reversal points is zero which means that velocity should be reduced from a value of above 40 m / min to zero over a short distance. This will probably result in mechanical problems of the deposition apparatus.

Problems solved by technology

High temperatures may lead to the inclusion of the undesirable OH groups in the external surface of the support tube.

Since the support tube forms part of the fibre yet to be drawn, it is to be expected that said included OH groups will present problems as regards the optical properties of the glass fibre that is eventually obtained.

It has become apparent that said OH groups produce adverse effects in the light conducting part of the optical fibre.

Moreover, said absorption peak at 1385 nm limits the use of the fibre over a large wavelength range that recent developments require.

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